Method And Apparatus For Cogeneration Heat Recovery

ABSTRACT

The present invention overcomes several disadvantages inherent in the operation of heat generating systems, particularly in the operation of engine-generators sets. The present apparatuses and methods increase the efficiency of these systems and provide means to economize fuel in their operation. The present invention applies to many type of engines and engines set combinations, but particularly to engine generator sets that run on fuels. Heat generating systems such as an engine-generator set are immersed in a medium similar, but not necessarily equal to, one used on oil cooled or liquid filled electrical transformers with high thermal conductivity and a high voltage rating. The medium in the unit recovers wasted heat (thermal energy). The heat recovered is transferred with a heat transfer unit or heat exchanger and utilized directly, as useful energy, for many purposes, such as heating, or cooling with the use of absorption or adsorption chillers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/519,638 filed 26 May 2011, the entire contents and substance of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to heat recovery from theoperation of a heat generating system immersed in a medium. Moreparticularly, the present invention relates to heat recovery, and thedampening of noise, generated by an internal combustion engine-generatorset, enclosed in a thermally insulated housing, and immersed in anon-combustible medium with a high heat transfer value and a high levelof electrical isolation capacity. The present invention allows recoveryof wasted heat energy from the engine-generator set and dampens noisegenerated by the engine-generator set.

2. Description of the Related Art

Engine-generator sets are used in countless applications where a readysource of electrical power is either inconvenient or unavailable. Thesesets are often used at construction sites, or outdoors where adverseweather conditions are unpredictable or unavoidable. Engine-generatorsets are also often used as backup electrical power sources atbusinesses and homes. In these types of conditions, loss of electricalpower due to the failure of the engine-generator set can result in asignificant economic loss. Therefore, reliability of the components isextremely important.

Internal combustion engines have been used to drive electric generatorsthat convert mechanical energy of the engines into electricity for usein the field for many purposes. One problem plaguing the use ofgenerator sets of this type is that these devices are noisy anduneconomical to operate. Since they must be run continuously to supplyelectricity, the noise generated by the internal combustion engine isunsuitable for many purposes, including their use in residential areas.Although many attempts have been made to enclose or house these units inspecial noise attenuation enclosures, these attempts have not beenentirely satisfactory because, in addition to other problems, the levelof noise reduction is not sufficient to effectively quiet the noise fromthe internal combustion engine. Noise abatement structures appliedexternally to the engine-generator set results in bulky and expensivenoise control systems. Enclosures or housings supplied to reduce noisealso tend to vibrate, thereby resulting in secondary noise emissions. Inaddition, problems have been experienced with the air cooling systems insuch enclosed generator sets.

Even though such enclosures have disadvantages, a housing surroundingthe engine-generator set does reduce the noise created by the operatingsystem, protect users from coming into contact with heated parts, andprotect the engine-generator set from adverse weather conditions. Yet byenclosing the heat generating components, such as the internalcombustion engine and alternator, with heat sensitive components, suchas the starting battery and electrical controls, serious reliabilityissues arise.

Using an air cooled engine for a small enclosed stand-byengine-generator set is very cost effective compared to fluid cooledengines, however using an air cooled engine creates significant designissues related to purging the housing of the air rejected from an aircooled engine. Another significant design issue is to prevent heated airfrom recirculation back into the engine air intake, especially in areascontaining heat sensitive components.

While noise and housing problems exist, another potentially more seriousproblem with the present design of electrical generator sets is thatwhile a generator set is in operation, approximately 60 to 70 percent ofthe fuel used in the engine is converted into waste heat. This wasteheat, or waste energy, is dissipated and lost into the atmosphere, orexpelled as unburned hydrocarbons. This waste heat severely limits theefficiency of the generator set. If recovered, the conventionally wastedheat could be used, for example, for heating a building during thewinter months or through an absorption or adsorption chiller to cool thesame building during the summer months. Thus, it can be seen that thereis a need for a method and apparatus that can both provide electricpower and heat recovery for cogeneration and a quieter system as well.

The present invention provides a method and apparatus for improving theefficiency of the operation of an electrical engine-generator set. Thepresent invention further provides a method for recuperating, andefficiently using, the waste heat produced by the conventional internalcombustion engine and the electrical generator during the operation ofthe system. The present invention further provides a method andapparatus for dampening the noise generated by the operation of anelectrical engine-generator set. The present invention further providesa weather resistant enclosure that provides an improved heat recoverysystem.

BRIEF SUMMARY OF THE INVENTION

Various embodiments of the present invention are directed towardsapparatuses and methods for recovering heat generated during theoperation of a heat generating system.

Broadly described, an aspect of the present invention comprises athermally insulated housing at least partially enclosing a heatgenerating system, a medium in heat transfer communication with at leasta portion of the heat generating system, and a heat recovery subsystemto recover heat from the medium. The medium can comprise a heatadsorbing, high-voltage rated, fluid. In an embodiment of the presentinvention, the heat recovery subsystem can comprise a heat exchanger. Inanother embodiment of the present invention, the heat generating systemcan comprise an engine-generator set. The recovered heat can betransferred to an adsorption chiller. In another embodiment of thepresent invention, the recovered heat can be transferred to a heater.

In another embodiment of the present invention, a method of recoveringheat from a heat generating system can comprise: providing a mediumcapable of transferring heat, in heat transfer communication with atleast a portion of a heat generating system, transferring heat from theheat generating system to the medium, and recovering heat from themedium. The medium can comprises a heat adsorbing, high-voltage rated,fluid. In an embodiment of the present invention, the transferring ofheat from the heat generating system to the medium can comprise the useof a heat exchanger. In another embodiment, the heat may be transferredto a device capable of utilizing heat from the medium. The heatgenerating system can comprise an engine-generator set.

In another embodiment of the present invention, an apparatus for therecovery of heat and dampening of noise generated during the operationof an engine-generator set can comprise: a thermally insulated housingat least partially enclosing an engine-generator set, a medium in heattransfer communication with at least a portion of the engine-generatorset, a dampening subsystem to dampen at least a portion of the noisegenerated by the engine-generator set, and a heat recovery subsystem torecover heat from the medium. The medium can comprise a heat adsorbing,high-voltage rated, medium. In an embodiment of the present invention,the heat recovery subsystem can comprise a heat exchanger. In anotherembodiment of the present invention, the medium can be in heat transfercommunication with at least a portion of exhaust generated by theengine-generator set. In another embodiment of the present invention, atleast a portion of medium passes through the generator via aperturestherein. In an embodiment of the present invention, the dampeningsubsystem can comprise a muffler. In another embodiment of the presentinvention, the dampening subsystem can comprise at least a portion ofthe medium.

In another embodiment of the present invention, at least one componentof the set can be not enclosed in the thermally insulated housing. Therecovered heat can be transferred to an adsorption chiller. In anotherembodiment of the present invention, the recovered heat can betransferred to a heater.

BRIEF DESCRIPTION OF THE FIGURES

The various embodiments of the invention can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the various embodiments of the presentinvention. In the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a side, sectional view of a preferred embodiment of thepresent invention where an engine-generator set is surrounded by athermally insulated housing, and completely immersed in medium,according to an exemplary embodiment of the present invention.

FIG. 2 is a side, sectional view of another preferred embodiment of thepresent invention where an exhaust pipe guides exhaust gases into amuffler, according to an exemplary embodiment of the present invention.

FIG. 3 is a side, sectional view of the flow pattern of heat absorbingmedium according to the proposed embodiment of the invention shown inFIG. 1.

FIG. 4 is a side, sectional view of a heat exchanger, according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Although preferred embodiments of the invention are explained in detail,it is to be understood that other embodiments are contemplated.Accordingly, it is not intended that the invention is limited in itsscope to the details of construction and arrangement of components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments and of being practiced orcarried out in various ways. Also, in describing the preferredembodiments, specific terminology will be resorted to for the sake ofclarity.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise.

Also, in describing the preferred embodiments, terminology will beresorted to for the sake of clarity. It is intended that each termcontemplates its broadest meaning as understood by those skilled in theart and includes all technical equivalents which operate in a similarmanner to accomplish a similar purpose.

By “comprising” it is meant that at least the named element, or methodstep is present in the apparatus or method, but does not exclude thepresence of other compounds, materials, particles, method steps, even ifthe other such compounds, material, particles, method steps have thesame function as what is named.

It is also to be understood that the mention of one or more method stepsdoes not preclude the presence of additional method steps or interveningmethod steps between those steps expressly identified. Similarly, it isalso to be understood that the mention of one or more components in adevice or system does not preclude the presence of additional componentsor intervening components between those components expressly identified.

Various embodiments of the present invention are directed towardsapparatuses and methods for recovering heat generated during theoperation of a heat generating system.

An embodiment of the present invention is an apparatus comprising athermally insulated housing at least partially enclosing a heatgenerating system, a medium in heat transfer communication with at leasta portion of the heat generating system, and a heat recovery subsystemto recover heat from the medium.

In an embodiment of the present invention, the heat generating systemcan comprise an engine-generator set. FIG. 1 shows the present inventionin a preferred embodiment of the set 10, comprising an engine 20 thatdrives a generator 30, both of which are contained within a thermallyinsulated housing 100. The thermally insulated housing 100 is filledwith a heat absorbing, high voltage rated, medium 90. Preferably theengine 20 is a conventional internal combustion engine modified to runon natural gas, although the same could run on any type of fuel if soequipped. The generator set is used to supply electrical power todesignated areas or equipments.

As illustrated in FIG. 1, the present unit engine-generator set can becompletely immersed in a medium 90. The heat generated by theconventional engine-generator set that is typically lost as waste heatis recovered by the medium 90 in which the engine-generator set isimmersed.

The medium 90 serves to internally cool the entire set 10, in particularthe engine 20 and the generator 30. The medium 90 also serves to absorbheat from the exhaust gases of the engine 20 by means of a heatexchanger 32.

The term “medium” is used herein for convenience and refers genericallyto many solids, liquids, gases, solutions, suspensions, powders, gels,dispersions, or combination thereof comprising at least one of theforegoing. The medium 90 should be high voltage resistant with good heatabsorbing qualities, and the housing 100 should be thermally insulatedto the external ambient. The medium should comprises coolingcharacteristics similar or better than the medium used to coolelectrical high voltage transformers, with high voltage rating andexcellent heat absorbing characteristics. The medium can comprise stablesilicon-based or fluorinated hydrocarbons, combustion-resistantvegetable oil-based dielectric coolants, synthetic pentaerythritol tetrafatty acid esters, or naphthenic mineral oil.

As shown in FIG. 1, internal combustion engine 20 draws air from theatmosphere through an intake pipe 22 having an air filter 24, whereambient air serves as the combustion air for engine 20. Intake pipe 22protrudes through and above the hermetically closed housing 100.

The engine exhaust pipe 26 also protrudes through and out of housing100.

In another embodiment of the present invention, the heat recoverysubsystem can comprise a heat exchanger. As shown in FIG. 2, exhaustpipe 26 can guide exhaust gases from internal combustion engine 20,after passing through heat recovery unit 32, into a muffler 62, whichdampens the noise of the set 10. Hot exhaust gases exit muffler 62through muffler exhaust pipe 64. The muffler exhaust pipe 64 expels theexhaust gases into the atmosphere. The heat recovery unit 32 transferredthe recovered heat into medium 90.

Cooling of engine 20 and generator 30 is provided by the surroundingmedium 90, which is pumped throughout the system using pump 34. Thusneither units, engine 20 nor generator 30, need to incorporateindividual cooling methods.

In another embodiment of the present invention, as shown in FIG. 1 andFIG. 3, medium 90 is sucked into the system by pump 34 through inlet 36.Pump 34 can be driven directly from engine 20 or through an alternatemethod. Medium 90 continues to flow through heat exchanger intake 38 toheat exchanger 32. Upon exiting the heat exchanger 32, medium 90 can bedirected to an end user or device through supply line 52 or pumped backto the housing 100. The end device can be, for example, an absorptionchiller (to cool) or to an air handling unit (to heat), or to any otherdevice or means of utilizing the recovered heat energy.

In the event of an air-cooled engine 20, pump 34 can serve to pump themedium 90 through a special set of baffles (not shown) that forces themedium 90 through a set of fins (not shown) that are conventionallyincorporated around the engine 20 in order to cool the engine 20 by theflow of medium 90. Medium 90 is also forced through generator 30 torecover the heat generated by this unit during its operation.

Generally the preferred embodiments are shown as FIG. 1-4 of the presentinvention, however it will be understood by those skilled in the artthat components of the present invention shown inside the housing 100(thus immersed in medium 90) can be located outside the housing 100, andconversely, some of those elements shown outside housing 100 can belocated inside housing 100. Only the engine 20 and generator 30 andappropriate piping must be immersed in medium 90. For example, heatexchanger 32 can be inside or outside housing 100, as can muffler 62,air filter 24, pump 42 or flow control valve 44. All heat generated bythe various components inside housing 100 is absorbed by medium 90. In apreferred embodiment, medium 90 exits housing 100, transfers its heat toan end device, or ambient, and return to set 10 through pipe 54 tocontinue the constant heat exchange with the submerged components. Inanother preferred embodiment shown in FIG. 4, the heat generated insidehousing 100 can be directly transferred into a medium by means of a heatexchanger (H) build right into the housing 100. This way the mediumneeded to cool the combination engine-generator set can be restricted tohousing 100 and the medium to be utilized in heat recovery could beused, by means of pump (K), to transfer the recovered heat to do usefulwork outside the housing 100.

The means for passing the medium 90 through the heat exchanger 32 isillustrated in FIG. 1 and FIG. 2, and described as preferably comprisingpump 34, intake 36 and exchanger intake 38. Other embodiments of themeans of passing the medium 90 through the heat exchanger 32 include anadditional pump at the intake of heat exchanger 32 or running thereturning medium from pipe 54 directly to the exhaust heat exchanger 32and discharging the medium 90 back into the housing 100. In the eventthat the medium 90 inside the housing 100 becomes too hot, a flowcontrol valve 44 can reroute medium 90, totally or partially, throughradiator 46. Radiator fan 48 can dissipate the heat of medium 90 intothe surrounding space, and medium 90 can be returned into housing 100.

The electrical generator 30 can be a high efficiency alternator typethat supplies alternating current to an electronic section, not shown,in enclosure 100. The electronic section can transform the suppliedalternating current into a stabilized alternating current with a desiredvoltage and or frequency or into a stabilized direct current with adesired voltage. A constant speed, brushless generator is alsocontemplated maintaining the output frequency at a constant value of 50or 60 cycles, as desired.

In a preferred embodiment, electrical generator 30 has a rotor withpermanent magnets, or brushless, and openings for passing cooling mediumthrough the inside of the unit. The stator of the electrical generatorcarries the electrical windings and includes sufficient clearance to letthe cooling medium 90 flow freely throughout the unit.

Electrical heaters 60 and 61 shown in FIG. 1 will come into operation,individually, by means of relays if additional thermal energy isrequired. They will operate directly from the electric power generatedby the unit otherwise the electric power generated will be sold to thepower company.

It should be understood, of course, that the foregoing relates only topreferred embodiments of the present invention and that numerousmodifications or alterations may be made therein without departing fromthe spirit and the scope of the invention as set forth in the claims.

1. An apparatus for the recovery of heat generated during the operationof a heat generating system, comprising: a thermally insulated housingat least partially enclosing a heat generating system; a medium in heattransfer communication with at least a portion of the heat generatingsystem; and a heat recovery subsystem to recover heat from the medium.2. The apparatus of claim 1, wherein the medium comprises a heatadsorbing, high-voltage rated, fluid.
 3. The apparatus of claim 1,wherein the heat recovery subsystem comprises a heat exchanger.
 4. Theapparatus of claim 1, wherein the heat generating system comprises anengine-generator set.
 5. The apparatus of claim 1, wherein recoveredheat is transferred to an adsorption chiller.
 6. The apparatus of claim1, wherein recovered heat is transferred to a heater.
 7. A method ofrecovering heat from a heat generating system, comprising: providing amedium capable of transferring heat, in heat transfer communication withat least a portion of a heat generating system; transferring heat fromthe heat generating system to the medium; and recovering heat from themedium.
 8. The method of claim 7, wherein the medium comprises a heatadsorbing, high-voltage rated, fluid.
 9. The method of claim 7, whereintransferring heat from the heat generating system to the mediumcomprises using a heat exchanger.
 10. The method of claim 7, furthercomprising transferring heat to a device capable of utilizing heat fromthe medium.
 11. The method of claim 7, wherein the heat generatingsystem comprises an engine-generator set.
 12. An apparatus for therecovery of heat and dampening of noise generated during the operationof an engine-generator set, comprising: a thermally insulated housing atleast partially enclosing an engine-generator set; a medium in heattransfer communication with at least a portion of the engine-generatorset; a dampening subsystem to dampen at least a portion of the noisegenerated by the engine-generator set; and a heat recovery subsystem torecover heat from the medium.
 13. The apparatus of claim 12, wherein themedium comprises a heat adsorbing, high-voltage rated, fluid.
 14. Theapparatus of claim 12, wherein the heat recovery subsystem comprises aheat exchanger.
 15. The apparatus of claim 12, wherein the medium is inheat transfer communication with at least a portion of exhaust generatedby the engine-generator set.
 16. The apparatus of claim 12, wherein atleast a portion of medium passes through the generator via aperturestherein.
 17. The apparatus of claim 12, wherein the dampening subsystemcomprises a muffler.
 18. The apparatus of claim 12, wherein thedampening subsystem comprises at least a portion of the medium.
 19. Theapparatus of claim 12, wherein at least one component of the set is notenclosed in the thermally insulated housing.
 20. The apparatus of claim12, wherein recovered heat is transferred to an adsorption chiller. 21.The apparatus of claim 12, wherein recovered heat is transferred to aheater.